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El-Khoury C, Mansour E, Yuliandra Y, Lai F, Hawkins BA, Du JJ, Sundberg EJ, Sluis-Cremer N, Hibbs DE, Groundwater PW. The role of adjuvants in overcoming antibacterial resistance due to enzymatic drug modification. RSC Med Chem 2022; 13:1276-1299. [PMID: 36439977 PMCID: PMC9667779 DOI: 10.1039/d2md00263a] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 09/16/2022] [Indexed: 02/03/2023] Open
Abstract
Antibacterial resistance is a prominent issue with monotherapy often leading to treatment failure in serious infections. Many mechanisms can lead to antibacterial resistance including deactivation of antibacterial agents by bacterial enzymes. Enzymatic drug modification confers resistance to β-lactams, aminoglycosides, chloramphenicol, macrolides, isoniazid, rifamycins, fosfomycin and lincosamides. Novel enzyme inhibitor adjuvants have been developed in an attempt to overcome resistance to these agents, only a few of which have so far reached the market. This review discusses the different enzymatic processes that lead to deactivation of antibacterial agents and provides an update on the current and potential enzyme inhibitors that may restore bacterial susceptibility.
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Affiliation(s)
- Christy El-Khoury
- Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney Sydney NSW 2006 Australia
| | - Elissar Mansour
- Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney Sydney NSW 2006 Australia
| | - Yori Yuliandra
- Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney Sydney NSW 2006 Australia
| | - Felcia Lai
- Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney Sydney NSW 2006 Australia
| | - Bryson A Hawkins
- Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney Sydney NSW 2006 Australia
| | - Jonathan J Du
- Department of Biochemistry, Emory University School of Medicine Atlanta GA 30322 USA
| | - Eric J Sundberg
- Department of Biochemistry, Emory University School of Medicine Atlanta GA 30322 USA
| | - Nicolas Sluis-Cremer
- Division of Infectious Diseases, Department of Medicine, University of Pittsburgh School of Medicine Pittsburgh PA 15213 USA
| | - David E Hibbs
- Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney Sydney NSW 2006 Australia
| | - Paul W Groundwater
- Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney Sydney NSW 2006 Australia
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2
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Alcala A, Ramirez G, Solis A, Kim Y, Tan K, Luna O, Nguyen K, Vazquez D, Ward M, Zhou M, Mulligan R, Maltseva N, Kuhn ML. Structural and functional characterization of three Type B and C chloramphenicol acetyltransferases from Vibrio species. Protein Sci 2019; 29:695-710. [PMID: 31762145 DOI: 10.1002/pro.3793] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2019] [Revised: 11/22/2019] [Accepted: 11/22/2019] [Indexed: 12/19/2022]
Abstract
Chloramphenicol acetyltransferases (CATs) were among the first antibiotic resistance enzymes identified and have long been studied as model enzymes for examining plasmid-mediated antibiotic resistance. These enzymes acetylate the antibiotic chloramphenicol, which renders it incapable of inhibiting bacterial protein synthesis. CATs can be classified into different types: Type A CATs are known to be important for antibiotic resistance to chloramphenicol and fusidic acid. Type B CATs are often called xenobiotic acetyltransferases and adopt a similar structural fold to streptogramin acetyltransferases, which are known to be critical for streptogramin antibiotic resistance. Type C CATs have recently been identified and can also acetylate chloramphenicol, but their roles in antibiotic resistance are largely unknown. Here, we structurally and kinetically characterized three Vibrio CAT proteins from a nonpathogenic species (Aliivibrio fisheri) and two important human pathogens (Vibrio cholerae and Vibrio vulnificus). We found all three proteins, including one in a superintegron (V. cholerae), acetylated chloramphenicol, but did not acetylate aminoglycosides or dalfopristin. We also determined the 3D crystal structures of these CATs alone and in complex with crystal violet and taurocholate. These compounds are known inhibitors of Type A CATs, but have not been explored in Type B and Type C CATs. Based on sequence, structure, and kinetic analysis, we concluded that the V. cholerae and V. vulnificus CATs belong to the Type B class and the A. fisheri CAT belongs to the Type C class. Ultimately, our results provide a framework for studying the evolution of antibiotic resistance gene acquisition and chloramphenicol acetylation in Vibrio and other species.
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Affiliation(s)
- Ashley Alcala
- San Francisco State University, Department of Chemistry and Biochemistry, San Francisco, California
| | - Guadalupe Ramirez
- San Francisco State University, Department of Chemistry and Biochemistry, San Francisco, California
| | - Allan Solis
- San Francisco State University, Department of Chemistry and Biochemistry, San Francisco, California
| | - Youngchang Kim
- Center for Structural Genomics of Infectious Diseases, Consortium for Advanced Science and Engineering, University of Chicago, Chicago, Illinois.,Structural Biology Center X-ray Science Division Argonne National Laboratory, Argonne, Illinois
| | - Kemin Tan
- Center for Structural Genomics of Infectious Diseases, Consortium for Advanced Science and Engineering, University of Chicago, Chicago, Illinois.,Structural Biology Center X-ray Science Division Argonne National Laboratory, Argonne, Illinois
| | - Oscar Luna
- San Francisco State University, Department of Chemistry and Biochemistry, San Francisco, California
| | - Karen Nguyen
- San Francisco State University, Department of Chemistry and Biochemistry, San Francisco, California
| | - Daniel Vazquez
- San Francisco State University, Department of Chemistry and Biochemistry, San Francisco, California
| | - Michael Ward
- San Francisco State University, Department of Chemistry and Biochemistry, San Francisco, California
| | - Min Zhou
- Center for Structural Genomics of Infectious Diseases, Consortium for Advanced Science and Engineering, University of Chicago, Chicago, Illinois.,Structural Biology Center X-ray Science Division Argonne National Laboratory, Argonne, Illinois
| | - Rory Mulligan
- Center for Structural Genomics of Infectious Diseases, Consortium for Advanced Science and Engineering, University of Chicago, Chicago, Illinois.,Structural Biology Center X-ray Science Division Argonne National Laboratory, Argonne, Illinois
| | - Natalia Maltseva
- Center for Structural Genomics of Infectious Diseases, Consortium for Advanced Science and Engineering, University of Chicago, Chicago, Illinois.,Structural Biology Center X-ray Science Division Argonne National Laboratory, Argonne, Illinois
| | - Misty L Kuhn
- San Francisco State University, Department of Chemistry and Biochemistry, San Francisco, California
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3
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Schwarz S. Emerging chloramphenicol resistance in Staphylococcus lentus from mink following chloramphenicol treatment: characterisation of the resistance genes. Vet Microbiol 1994; 41:51-61. [PMID: 7801525 DOI: 10.1016/0378-1135(94)90135-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A total of 26 staphylococcal strains isolated from mink with urinary tract infections as well as from the environment of the mink were examined for antibiotic resistance and prevalence of plasmids mediating resistance to the antibiotics applied for prophylactic or therapeutic purposes. Chloramphenicol resistance (Cmr) which occurred in fourteen of the eighteen Staphylococcus lentus strains, but in none of the Staphylococcus intermedius and Staphylococcus xylosus strains, was shown to be mediated by small plasmids of 3.6 to 4.6 kb. On the basis of restriction endonuclease mapping and hybridization experiments, four different types of Cmr plasmids, designated pSCS14-17, could be distinguished. All these plasmids conferred Cmr by encoding the Cm-inactivating enzyme chloramphenicol acetyltransferase (CAT). In all four types of Cmr plasmids from S. lentus, the expression of the cat gene was inducible with Cm, as demonstrated by enzymatic assay and polyacrylamide gel electrophoresis.
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Affiliation(s)
- S Schwarz
- Institut für Kleintierforschung der Bundesforschungsanstalt für Landwirtschaft (FAL), Celle, Germany
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4
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Schwarz S, Cardoso M. Molecular cloning, purification, and properties of a plasmid-encoded chloramphenicol acetyltransferase from Staphylococcus haemolyticus. Antimicrob Agents Chemother 1991; 35:1277-83. [PMID: 1929282 PMCID: PMC245158 DOI: 10.1128/aac.35.7.1277] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
A small chloramphenicol resistance (Cmr) plasmid of approximately 3.75 kb, designated pSCS5, was isolated from Staphylococcus haemolyticus. This plasmid encoded an inducible chloramphenicol acetyltransferase (CAT; EC 2.3.1.28). The cat gene of pSCS5 was cloned into the Escherichia coli plasmid vector pBluescript SKII+. It differed in its nucleotide sequence and deduced amino acid sequence from the cat genes described previously in staphylococci and other gram-positive bacteria. The CAT enzyme was purified from cell-free lysates by ammonium sulfate precipitation, ion-exchange chromatography, and fast protein liquid chromatography. The native enzyme had an Mr of 70,000 and was composed of three identical subunits, each with an Mr of approximately 23,000. Its isoelectric point was at pH 6.15. CAT from pSCS5 exhibited Km values of 2.81 and 51.8 microM for chloramphenicol and acetyl coenzyme A, respectively. The optimum pH for activity was 7.8. CAT encoded by pSCS5 proved to be relatively heat stable, but sensitive to mercury ions. The observed differences in the nucleotide sequence and the biochemical characteristics of the enzyme allowed the identification of the pSCS5-encoded CAT from S. haemolyticus as a CAT variant different from those described previously in gram-positive bacteria.
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Affiliation(s)
- S Schwarz
- Institut für Bakteriologie und Immunologie, Justus Liebig Universität Giessen, Federal Republic of Germany
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5
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Russell GC, Guest JR. Site-directed mutagenesis of the lipoate acetyltransferase of Escherichia coli. Proc Biol Sci 1991; 243:155-60. [PMID: 1676519 DOI: 10.1098/rspb.1991.0025] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Remote but significant similarities between the primary and predicted secondary structures of the chloramphenicol acetyltransferases (CAT) and lipoate acyltransferase subunits (LAT, E2) of the 2-oxo acid dehydrogenase complexes, have suggested that both types of enzyme may use similar catalytic mechanisms. Multiple sequence alignments for CAT and LAT have highlighted two conserved motifs that contain the active-site histidine and serine residues of CAT. Site-directed replacement of Ser550 in the E2p subunit (LAT) of the pyruvate dehydrogenase complex of Escherichia coli, deemed to be equivalent to the active-site Ser148 of CAT, supported the CAT-based model of LAT catalysis. The effects of other substitutions were also consistent with the predicted similarity in catalytic mechanism although specific details of active-site geometry may not be conserved.
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Affiliation(s)
- G C Russell
- Krebs Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, U.K
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6
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Laredo J, Wolff VL, Lovett PS. Chloramphenicol acetyltransferase specified by cat-86: relationship between the gene and the protein. Gene 1988; 73:209-14. [PMID: 3149605 DOI: 10.1016/0378-1119(88)90327-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Gene cat-86 is chloramphenicol (Cm)-inducible and specifies Cm acetyltransferase, CAT-86. The gene was previously cloned from the DNA of a strain of Bacillus pumilus. In the present study we report the construction of a constitutively expressed version of cat-86 that permits high-level expression of the gene on a plasmid in B. subtilis. A method is described that allows very rapid purification of CAT-86 protein to homogeneity. The sequence of 13 N-terminal amino acids of purified CAT-86, as well as the 26.6-kDa size of the subunit protein, agree with predictions made based on the nucleotide sequence of the gene. The Mr of the native enzyme suggests that CAT-86 is a trimer consisting of three identical protein subunits. Our studies demonstrate that cat-86 provides a convenient system for analyzing relationships between a gene and a multimeric enzyme in the B. subtilis background.
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Affiliation(s)
- J Laredo
- Department of Biological Sciences, University of Maryland Baltimore County, Catonsville 21228
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8
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Charles IG, Harford S, Brookfield JF, Shaw WV. Resistance to chloramphenicol in Proteus mirabilis by expression of a chromosomal gene for chloramphenicol acetyltransferase. J Bacteriol 1985; 164:114-22. [PMID: 3900034 PMCID: PMC214218 DOI: 10.1128/jb.164.1.114-122.1985] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Proteus mirabilis PM13 is a well-characterized chloramphenicol-sensitive isolate which spontaneously gives rise to resistant colonies on solid media containing chloramphenicol (50 micrograms ml-1) at a plating efficiency of 10(-4) to 10(-5). Such chloramphenicol-resistant colonies exhibit a novel phenotype with respect to chloramphenicol resistance. When a single colony grown on chloramphenicol agar is transferred to liquid medium and grown in the absence of antibiotic for 150 generations, a population of predominantly sensitive cells arises. This mutation-reversion phenomenon has been observed in other Proteus species and Providencia strains, wherein resistance has been shown to be mediated in each case by the enzyme chloramphenicol acetyltransferase. The cat gene responsible for the phenomenon is chromosomal and can be cloned from P. mirabilis PM13 with DNA prepared from cells grown in the absence or the presence of chloramphenicol. Recombinant plasmids which confer resistance to chloramphenicol carry an 8.5-kilobase PstI fragment irrespective of the source of host DNA. The location of the cat gene within the PstI fragment was determined by Southern blotting with a cat consensus oligonucleotide corresponding to the expected amino acid sequence of the active site region of chloramphenicol acetyltransferase, and the direction of transcription was deduced from homology with the type I cat variant.
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9
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Kleanthous C, Cullis PM, Shaw WV. 3-(Bromoacetyl)chloramphenicol, an active site directed inhibitor for chloramphenicol acetyltransferase. Biochemistry 1985; 24:5307-13. [PMID: 3865688 DOI: 10.1021/bi00341a006] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Bacterial resistance to the antibiotic chloramphenicol is normally mediated by chloramphenicol acetyltransferase (CAT), which utilizes acetyl coenzyme A as the acyl donor in the inactivation reaction. 3-(Bromoacetyl)chloramphenicol, an analogue of the acetylated product of the forward reaction catalyzed by CAT, was synthesized as a probe for accessible and reactive nucleophilic groups within the active site. Extremely potent covalent inhibition was observed. Affinity labeling was demonstrated by the protection afforded by chloramphenicol at concentrations approaching Km for the substrate. Inactivation was stoichiometric, 1 mol of the inhibitor covalently bound per mole of enzyme monomer, with complete loss of both the acetylation and hydrolytic activities associated with CAT. N3-(Carboxymethyl)histidine was identified as the only alkylated amino acid, implicating the presence of a unique tautomeric form of a reactive imidazole group at the catalytic center. The proteolytic digestion of CAT modified with 3-(bromo[14C]-acetyl)chloramphenicol yielded three labeled peptide fractions separable by reverse-phase high-pressure liquid chromatography. Each peptide fraction was sequenced by fast atom bombardment mass spectrometry; the labeled peptide in each case was found to span the highly conserved region in the primary structure of CAT, which had been tentatively assigned as the active site. The rapid, stoichiometric, and specific alkylation of His-189, taken together with the high degree of conservation of the adjacent amino acid residues, strongly suggests a central role for His-189 in the catalytic mechanism of CAT.
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10
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Shaw WV, Brenner DG, Murray IA. Regulation of antibiotic resistance in bacteria: the chloramphenicol acetyltransferase system. CURRENT TOPICS IN CELLULAR REGULATION 1985; 26:455-68. [PMID: 3865758 DOI: 10.1016/b978-0-12-152826-3.50043-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The evaluations of antibiotic resistance has been a subject of interest to workers in several disciplines. Our current understanding of the molecular biology of plasmids, phages, and transposable elements provides a basis for appreciating the range of mechanisms likely to be involved in the horizontal spread of resistance determinants through microbial ecosystems. Rather less can be imagined with confidence about the origins of the genes or the constraints and selection pressures operating at the level of protein structure. The CAT system illustrates the extent of variation possible for an accessory gene product which is required infrequently and which is encoded by multicopy and promiscuous vectors which can cross taxonomic boundaries. Still less is known with certainty about the evolution of genetic control of the expression of antibiotic resistance. While there are sound reasons for looking in detail at prokaryotic antibiotic-producing organisms such as Streptomyces to find the progenitors of present resistance mechanisms (44, 45), it seems likely that controls of expression have been acquired during the "passage" of selectable markers through more distant bacterial genera. The CAT system is illustrative of the variety we may expect to find in control strategies used by microbial systems generally. It might indeed be a surprise to find an expression mechanism operating in the CAT system (or for any other family of resistance genes) which was not illustrative of a general strategy exploited by essential genes specifying biosynthetic or degradative functions. There may be some truth in referring to the cat structural gene as a "cartridge" for the isolation and manipulation of promoter functions. It would seem that nature has been at it for some time.
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11
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Shaw WV, Brenner DG, LeGrice SF, Skinner SE, Hawkins AR. Chloramphenicol acetyltransferase gene of staphylococcal plasmid pC221. Nucleotide sequence analysis and expression studies. FEBS Lett 1985; 179:101-6. [PMID: 3855295 DOI: 10.1016/0014-5793(85)80200-3] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The nucleotide sequence of the inducible chloramphenicol acetyltransferase gene (cat) of Staphylococcus aureus plasmid pC221 has been determined. The deduced primary structure for the 215 residue polypeptide (25.9 kDa) is in agreement with partial amino acid sequence data on the purified protein, previously designated as the type C variant of CAT. In common with the inducible cat elements of pC194 and B. pumilus, the 5' non-coding region of the cat of pC221 contains an inverted complementary repeat ('stem-loop' or 'hairpin') which may sequester the predicted ribosome bonding site of the mRNA. The likely transcription initiation site has been determined in vitro using purified B. subtilis RNA polymerase. Recombinant plasmids carrying the cat of pC221 on a 1156 bp TaqI fragment are expressed inefficiently in Escherichia coli, wherein induction is both poor and orientation-specific.
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12
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Duvall EJ, Williams DM, Lovett PS, Rudolph C, Vasantha N, Guyer M. Chloramphenicol-inducible gene expression in Bacillus subtilis. Gene 1983; 24:171-7. [PMID: 6416927 DOI: 10.1016/0378-1119(83)90077-x] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
A cloned Bacillus pumilus cat gene expresses chloramphenicol-inducible chloramphenicol acetyltransferase activity in Bacillus subtilis. The chloramphenicol inducibility trait was shown to be determined by a 234-bp region of the cloned DNA. Nucleotide sequence analysis of this 234-bp segment indicated that the cat ribosome-binding site occurs within a 40-bp region containing 14-bp terminal inverted repeat sequences. Transcription of this region into RNA should sequester the cat ribosome-binding site in a stable stem-loop conformation. Chloramphenicol-mediated destabilization of the stem-loop is suggested as the basis for the chloramphenicol inducibility phenotype.
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13
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Foster TJ. Plasmid-determined resistance to antimicrobial drugs and toxic metal ions in bacteria. Microbiol Rev 1983; 47:361-409. [PMID: 6355806 PMCID: PMC281581 DOI: 10.1128/mr.47.3.361-409.1983] [Citation(s) in RCA: 168] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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14
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Shaw WV. Chloramphenicol acetyltransferase: enzymology and molecular biology. CRC CRITICAL REVIEWS IN BIOCHEMISTRY 1983; 14:1-46. [PMID: 6340955 DOI: 10.3109/10409238309102789] [Citation(s) in RCA: 180] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Naturally occurring chloramphenicol resistance in bacteria is normally due to the presence of the antibiotic inactivating enzyme chloramphenicol acetyltransferase (CAT) which catalyzes the acetyl-S-CoA-dependent acetylation of chloramphenicol at the 3-hydroxyl group. The product 3-acetoxy chloramphenicol does not bind to bacterial ribosomes and is not an inhibitor of peptidyltransferase. The synthesis of CAT is constitutive in E. coli and other Gram-negative bacteria which harbor plasmids bearing the structural gene for the enzyme, whereas Gram-positive bacteria such as staphylococci and streptococci synthesize CAT only in the presence of chloramphenicol and related compounds, especially those with the same stereochemistry of the parent compound and which lack antibiotic activity and a site of acetylation (3-deoxychloramphenicol). Studies of the primary structures of CAT variants suggest a marked degree of heterogeneity but conservation of amino acid sequence at and near the putative active site. All CAT variants are tetramers composed in each case of identical polypeptide subunits consisting of approximately 220 amino acids. The catalytic mechanism does not appear to involve an acyl-enzyme intermediate although one or more cysteine residues are protected from thiol reeagents by substrates. A highly reactive histidine residue has been implicated in the catalytic mechanism.
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15
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Chapter 13. Mechanisms of Antibiotic Resistance. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 1982. [DOI: 10.1016/s0065-7743(08)60495-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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16
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Wilson CR, Skinner SE, Shaw WV. Analysis of two chloramphenicol resistance plasmids from Staphylococcus aureus: insertional inactivation of Cm resistance, mapping of restriction sites, and construction of cloning vehicles. Plasmid 1981; 5:245-58. [PMID: 6267630 DOI: 10.1016/0147-619x(81)90002-0] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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17
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Packman LC, Shaw WV. Identification of "buried" lysine residues in two variants of chloramphenicol acetyltransferase specified by R-factors. Biochem J 1981; 193:525-39. [PMID: 6796049 PMCID: PMC1162634 DOI: 10.1042/bj1930525] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Two variants of chloramphenicol acetyltransferase which are specified by genes on plasmids found in Gram-negative bacteria were subjected to amidination with methyl acetimidate to determine the relative reactivity of surface lysine residues and to search for unreactive or "buried" amino groups which might contribute to stabilization of the native tetramers. Representative examples of the type-I and type-III variants of chloramphenicol acetyltransferase were found to have one lysine residue each in the native state which appears to be inaccessible to methyl acetimidate. The uniquely unreactive residue of the type-I protein is lysine-136, whereas the lysine that is "buried" in the type-III enzyme is provisonally assigned to residue 38 of the prototype sequence. It is suggested that the lysine residue in each case participates in the formation of an ion pair at the intersubunit interface and that the two amino groups in question occupy functionally equivalent positions in the quaternary structures of their respective enzyme variants. Lysine-136 of type-I enzyme is also uniquely unavailable for modification by citraconic anhydride, a reagent used to disrupt the quaternary structure of the native enzyme. Contrary to expectation, exhaustive citraconylation fails to dissociate the tetramer, but does destroy catalytic activity. Removal of citraconyl groups from modified chloramphenicol acetyltransferase is accompanied by a full region of catalytic activity. Analysis of the rate of hydrolysis of citraconyl groups from the modified tetramer by amidination of unblocked amino groups with methyl [14C]acetamidate reveals difference in lability for several of the ten modified lysine residues. Although the unique stability of the quaternary structure of chloramphenicol acetyltransferase may be due to strong hydrophobic interactions, it is argued that lysine-136 may contribute to stability via the formation of an ion pair at the subunit interface.
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18
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Fitton JE, Dell A, Shaw WV. The amino acid sequence of the delta haemolysin of Staphylococcus aureus. FEBS Lett 1980; 115:209-12. [PMID: 7398877 DOI: 10.1016/0014-5793(80)81170-7] [Citation(s) in RCA: 118] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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19
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Nitzan Y, Gozhansky S. Chloramphenicol binding site of an fi- R-factor-specified variant of chloramphenicol acetyltransferase. Arch Biochem Biophys 1980; 201:115-20. [PMID: 6994649 DOI: 10.1016/0003-9861(80)90494-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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20
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Shaw WV, Packman LC, Burleigh BD, Dell A, Morris HR, Hartley BS. Primary structure of a chloramphenicol acetyltransferase specified by R plasmids. Nature 1979; 282:870-2. [PMID: 390404 DOI: 10.1038/282870a0] [Citation(s) in RCA: 119] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Naturally occurring isolates of chloramphenicol-resistant bacteria commonly synthesise chloramphenicol acetyltransferase (EC 2.3.28; CAT) in amounts which are sufficient to account for the resistance phenotype and often harbour plasmids which carry the structural gene for CAT. The findings of CAT in such diverse prokaryotes as Proteus mirabilis, Agrobacterium tumefaciens, Streptomyces sp., and a soil Flavobacterium has led to speculation concerning the origin and evolution of the more commonly observed CAT variants specified by plasmids in clinically important bacteria. To provide a more solid basis for studying the evolution and spread of CAT within prokaryotes we chose to determine the complete amino acid sequence of a type I variant of CAT, the variant known to be associated with most F-like plasmids conferring chloramphenicol resistance. The sequence has been determined by combining the results obtained from manual and automated sequential degradation with those obtained by mass spectrometry of peptides generated by enzymatic digestion. The directly determined primary structure is identical with that predicted by the DNA sequence analysis of the chloramphenicol resistance transponson Tn9 known to specify a type I variant of chloramphenicol acetyltransferase.
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21
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Zaidenzaig Y, Fitton JE, Packman LC, Shaw WV. Characterization and comparison of chloramphenicol acetyltransferase variants. EUROPEAN JOURNAL OF BIOCHEMISTRY 1979; 100:609-18. [PMID: 116849 DOI: 10.1111/j.1432-1033.1979.tb04208.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
1. Variants of chloramphenicol acetyltransferase from a variety of bacterial species have been isolated and purified to homogeneity. They constitute a heterogeneous group of proteins as judged by analytical affinity and hydrophobic ('detergent') chromatography, native and sodium dodecyl sulfate electrophoresis, sensitivity to sulfhydryl specific reagents, steady state kinetic analysis, and reaction with antisera. 2. The most striking observation is that three variants of chloramphenicol acetyltransferase (R factor type III, Streptomyces acrimycini, and Agrobacterium tumefaciens) possess an apparent subunit molecular weight (24,500) which is significantly greater than that of all other variants examined (22,500). The three atypical variants are not identical since they show marked differences in a number of important parameters. 3. Although the fundamental mechanism of catalysis may prove to be identical for all chloramphenicol acetyltransferase variants, there is a wide range of sensitivity to thiol-directed inhibitors among the enzymes studied. 4. Amino acid sequence analysis of the N-termini of selected variants suggests that the qualitative differences among chloramphenicol acetyltransferase variants is a reflection of structural heterogeneity which is most marked in comparisons between variants from Gram-positive and Gram-negative species.
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